In this installment of Ask a Marine Biologist, Dr. David Shiffman tackles a frequently asked question about sharks.
Question: How many species of sharks are there?
A shoal of sharks in South Africa.
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Answer: A lot of people are confused about this, and it’s easy to see why! A Google search of this question reveals a pretty wide range of answers. LiveScience reports that “there are more than 250 species of sharks.” PBS Nova claims “there are over 350 species of sharks.” Encyclopedia Britannica says there are 400. And SharkSider puts that number at more than 450. So what’s the real answer? According to a 2016 scientific publication with the snappy title “Annotated checklist of the living sharks, batoids and chimaeras (Chondrichthyes) of the world, with a focus on biogeographical diversity,” there are a total of 509 scientifically recognized species of sharks, which doesn’t count 630 species of skates and rays or 49 species of chimaeras. Sharks, skates, rays and chimaeras are closely related and form a group called the chondrichthyan fishes, whose skeletons are made of cartilage, distinct from the bony fishes of class Osteichthyes. “But what about elasmobranchs?” you ask, having read shark books as a kid. Elasmobranch fishes include sharks, skates and rays, but not chimaeras. (Chondrichthyes is a class—remember your kingdom, phylum, class, order, family, genus, species? Elasmobranchii is a subclass, as is the subclass Holocephalii, which contains the chimaeras.) Confusing right? That’s taxonomy for you.
So, is the answer 509 species of sharks? Well, not quite. That paper is three years old, and we are currently in the middle of a golden age of chondrichthyan taxonomy. More than 15% of all known species of sharks and their relatives have been described in the past decade or so, and there are several new species that have been described since 2016, like Genie’s dogfish, named after shark research pioneer Dr. Eugenie Clark. A new species of shark or other chondrichthyan is described, on average, every two weeks. (The press release for the coming-soon edition of the Sharks of the World reference guide refers to 525 shark species, for what it’s worth.) For now, the best answer I can give you is there are at least 509 scientifically recognized species of sharks, with more being described all the time. But ask me again when we get an updated annotated checklist of chondrichthyans published in the scientific literature!
Dr. David Shiffman
Courtesy David Shiffman
Ask a Marine Biologist is a biweekly column where Dr. David Shiffman answers your questions about the underwater world. Topics are chosen from reader-submitted queries as well as data from common internet searches. If you have a question you’d like answered in a future Ask a Marine Biologist column, or if you have a question about the answer given in this column, email Shiffman at WhySharksMatter@gmail.com with subject line “Ask a marine biologist.”
Dr. David Shiffman is a marine conservation biologist specializing in the ecology and conservation of sharks. An award-winning public science educator, David has spoken to thousands of people around the world about marine biology and conservation, and has bylines with the Washington Post, Scientific American, New Scientist, Gizmodo and more. Follow him on Twitter, Facebook and Instagram, where he’s always happy to answer any questions about sharks.